1. FIELD OF THE INVENTION
The present invention relates to a crop shear apparatus, and, more particularly to a crop shear apparatus for, in a widthwise direction of a band steel plate, shearing a crop formed in a lengthwise directional end portion, that is, in a conveyance directional end portion of the band steel plate rolled by a roughing-down or rough rolling mill of hot rolling equipment before it is rolled by a finish rolling mill.
2. DESCRIPTION OF THE RELATED ART
In order to meet a desire of preventing an undesirable or uneven contraction or reduction (a problem taken place in that the degree, at which a material is rolled, becomes nonuniform in the widthwise direction of the material due to the positional deviation of the material in the axial direction of the rolling mill) which will be taken place at the finish rolling operation performed in hot rolling equipment, there has been available a crop shear apparatus for shearing, as a crop, an irregular end portion such as a fish tail or a tongue formed in at least either of a leading end portion or a rear end portion of a band steel, which has been rolled by a rough rolling mill, in the widthwise direction of the band steel before the band steel is rolled by a finish rolling mill (for example, "Advanced Technology of Hot Strip Mill in Japan", p.p 31 to 32, Japanese Patent Unexamined Publication No. 1-310809 and Japanese Patent Unexamined Publication No. 60-201816). Another technology or use in an endless rolling operation has been known in which two band steel plates, the lengthwise end portions of which are positioned adjacent to each other, are connected to each other at the adjacent end portions before the band steel is subjected to the finish rolling (for example, Japanese Patent Unexamined Publication No. 60-231504).
At p.p 31 to 32 of "Advanced Technology of Hot Strip Mill in Japan", the following facts are disclosed:
(1) A crop shear is disposed in an inlet side of a finish rolling mill so as to cut a crop formed in the front and rear end portions of a bar rolled in the rough rolling process in order to remove defective portions, prevent undesirable contractions and as well as to prevent a surface of the roll from being recessed due to catch of material at a low temperature. PA1 (2) The crop shears are exemplified by a drum-type shear, a crank-type shear and a vibration-type shear. PA1 (3) The drum-type shears are exemplified by a single knife type shear having one shear blade mounted to one drum and a double knife type shear having two shear blades mounted to the same. PA1 (4) Either of the blades of the double knife type shear is used to shear the front end portion (leading end portion) of the bar or band steel, while the other blade is used to shear the rear end portion (trailing end portion) of the band steel. PA1 (5) An example of the double knife type crop shear is illustrated and disclosed in which a straight blade is used to serve as one of the two blades and a curved (circular-arc) blade, the radius of curvature of which is 13.843 m, is used to serve as the other shear blade. PA1 (1) The front and rear end portions of the two band steel plates are connected to each other by multi-layer build up welding. PA1 (2) The fillets formed by stacking the front and rear end portions of the two band steel plates are spotwelded to connect the adjacent front and the rear end portions of the two band steel plates. PA1 (3) The adjacent front and rear end portions of the two band steel plates are machined before they are stacked up and the machined two adjacent end portions of the two band steel plates are connected by a bolt.
However, if the widths of the band steel plates to be sheared are different from each other in a case where a circular-arc shear blade having constant radius of curvature is used, the degree of projection of a widthwise end portion of the band steel in the lengthwise direction of the band steel with respect to the widthwise directional central portion of the band steel, that is, a "projection quantity" becomes different (for example, in a case where the radius of curvature is 13.84 m, the projection quantity is 3.3 mm if the width of the band steel is 60 cm, while the projection quantity is 23.1 mm if the width of the band steel is 160 cm). However, the change in the planar shape of the end portion generated due to the finish rolling does not necessarily hold a positive correlation with the width of the band steel but it depends upon the cross sectional shape of the band steel to be finish-rolled.
However, at p.p 31 to 32 of "Advanced Technology of Hot Strip Mill in Japan", there is no description about the technology of adjusting the projection quantity of the shear front end portion of the band steel or the shear rear end portion of the same independent of the width of the band steel.
In Japanese Patent Application Laid-Open No. 1-310809, a technology has been disclosed in which the shear blade is formed into a curved shape when viewed in a direction perpendicular to the principal surface of the band steel such that the quantity of lapping of the upper shear blade of a drum-type crop shear and the lower shear blade of the same is made to be zero in the side end portions the widthwise directional end portions) of the band steel.
However, there is no description about the technology of adjusting the projection quantity of the shear front end portion of the band steel or the shear rear end portion of the same independent of the width of the band steel in Japanese Patent Application Laid-Open No. 1-310809.
In Japanese Patent Application Laid-Open No. 60-201816, a crop shear is disclosed which is capable of movably supporting the shear blade in the widthwise direction (in the axial direction of the drum) of the band steel in order to change portions of the shear blade which shear the side end portions of the band steel because the above-described portions of the shear blade for shearing the side end portions is likely to be broken if the same portion of the shear blade of the crop shear apparatus of the drum-type shear repeatedly shears a crop of the band steel having a constant width along the widthwise direction of the band steel.
However, in Japanese Patent Application Laid-Open No. 60-201816, a fact has been disclosed that shearing by using the same portion of the blade must be inhibited but there is no description about the necessity of determining the shape of the shear blade in accordance with the widthwise directional movement of the blade.
In Japanese Patent Application Laid-Open No. 60-231504, the following conventional technologies are described:
Furthermore, problems experienced with the above-described conventional technology are described in which the above-described connection took a relatively long time and and/or would increase the cost. In addition, a technology has been disclosed in which the two adjacent front and rear end portions of the two band steel plates, which have been sheared into shapes complementary to one another, are introduced into the finish rolling mill while maintaining the above-described two adjacent front and rear end portions at a state in which they are forcibly positioned in contact with each other so that the contact portions are metallurgically connected to each other at the time of the finish rolling process.
However, in the above-described case of the technology disclosed in Japanese Patent Unexamined Publication No. 60-231504 in which the complementarily shaped ends are forcibly positioned in contact with each other, the two adjacent front and rear end portions of the two band steel plates are not secured to each other before the finish rolling operation is performed. Therefore, the ends of the two band steel plates are not ensured to be kept in contact, and therefore are not ensured to be connected at the time of the finish rolling process.